The primary advantage in the use of zero insertion force connectors, namely, minimizing loading of interfitting contacts during connection, takes on particularly great significance as the number of contacts simultaneously made increases to levels today seen with circuit components produced by very large scale integration (VLSI) techniques. In this sector, a VLSI device may present a twenty-by-twenty pin array, i.e., a total of four hundred pins, for simultaneous individual mating with collectively supported sockets. The loading forces attending such connection are, of course, cumulative of the force per mating contact pair and can readily amount to a level which may be unattainable for an assembler or not sustainable by support housings of the respective pins and sockets.
A further problem presented to the connector designer by VLSI is that of readily facilitating connection and disconnection and while minimizing the space in which such insertion connection and disconnection are to be effected. Customary practices in the art in larger environs are not applicable. In the above example of VLSI connection, the twenty-by-twenty pin array may be necessary within a square of about two inches per side, i.e., about one-tenth inch pin spacings in both column and row directions. Further connections may envision forty-by-forty pin arrays or more.
There are generally two types of zero insertion force connectors, one in which the contacts are normally closed and the other in which the contacts are normally open. The present invention relates to a zero insertion force connector having normally closed contacts. There are a number of known zero insertion force connectors of the closed-contact type which are used to make connection to conductors on printed circuit boards as well as to the leads of electronic packages or components and which employ camming devices for opening such contacts. Such connectors for printed circuit board connections are shown, for example, in U.S. Pat. Nos. 4,196,955; 4,159,861; 4,159,154; 3,553,630; 3,426,313 and 3,395,377 and in German Pat. No. 1,118,852. References showing connections to a multi-pin device in a closed contact connector include U.S. Pat. Nos. 4,080,032 and 4,050,758, the latter reference also being useful in connections to printed circuit boards.
In commonly-assigned, U.S. Pat. No. 4,422,703, issued on Dec. 27, 1983 in the name of the same inventors as herein, there is disclosed an electrical connector of zero or low insertion force receipt of multi-pin arrays such as those in VLSI components. Cam surfaces are employed for selective movement to oppose self-biasing forces of the connector contacts for pin insertion and reverse movement to permit the contacts to tightly engage the pins under the influence of the contact self-bias. While the connector shown therein contains attractive features and represents an advance in the art, the particular structure disclosed results in a height profile greater than that desired, particularly where pin connections in array greater than twenty-by-twenty are contemplated.